Squadron Leader Terry Hilliard, a Royal Air Force (RAF) pilot who played a key role in Britain’s thermonuclear weapons testing program in the late 1950s, died on April 24, 2026, at the age of 93.

Hilliard was notably involved in the Grapple Z series of British hydrogen bomb tests conducted near Christmas Island, now known as Kiritimati, in the South Pacific. On September 11, 1958, flying at over 53,000 feet in a modified Canberra bomber, he piloted one of four aircraft tasked with penetrating the radioactive mushroom cloud to collect fallout samples. These “sniffer planes” gathered vital data to help scientists assess the yield and effectiveness of the 800-kiloton thermonuclear device, which had an explosive power approximately 40 times that of the atomic bomb dropped on Nagasaki in 1945.

The mission pushed the Canberra bomber beyond its official altitude limits, requiring Hilliard and his two crew members to remain inside the turbulent and highly radioactive cloud for seven and a half minutes. Instruments onboard measured radiation exposure levels within the cockpit throughout the dangerous flight. Upon returning to base, Hilliard and his crew underwent decontamination procedures including radiation checks and ice-cold showers. One pilot on another flight was removed from duty due to high contamination levels.

Hilliard's contributions were part of a broader effort that established Britain as the world’s third thermonuclear power following the United States and the Soviet Union. These tests, conducted in 1958 with the support of RAF units based in Australia and the South Pacific, were critical in maintaining Britain’s strategic nuclear deterrent during the Cold War. The Canberra aircraft used in the tests also played a role in collecting fallout from nuclear tests conducted by other countries, such as the Soviet Union and China.

Born in Newport, Monmouthshire, in 1932, Hilliard joined the RAF in 1948, initially as an aircraft apprentice before training as a pilot. During his early service, he flew jet bombers in multiple operational theaters, including Malaya during counterinsurgency operations and Malta during the Suez Crisis in 1956. After his tour with 9 Squadron, he was promoted and posted to 76 Squadron, eventually flying V-bombers and serving in staff roles within Bomber Command.

Following his retirement from the RAF in 1969, Hilliard pursued a career in business, establishing an insurance firm, managing a hotel, and later contributing to business education ventures in Australia. He and his wife, Sally Smith, married in 1959 and had three children. Sally passed away in 2018.

Throughout his life, Hilliard expressed concerns about his exposure to radiation during the nuclear tests, describing the ongoing mental strain and health implications faced by many veterans of these operations. He survived non-Hodgkin’s lymphoma in 2017-2018, though the treatment caused additional health challenges including a heart attack and partial loss of eyesight.

Hilliard documented his experiences of the Grapple Z tests in recordings contributed to a museum exhibition, preserving the history of Britain’s atomic era. His family remembered him as a resilient and dedicated figure, proud of his RAF service and his role in a defining period of national defense history.